The Sunsoft FME-7 is a mapper IC used by Sunsoft in several of its games. It is nearly identical to the Sunsoft 5A and Sunsoft 5B mapper chips used only in Famicom games, with the 5B notably having expansion audio (see Sunsoft 5B audio).

In Europe, boards using the FME-7 were labeled as JSROM and JLROM. The FME-7 mapper was used in only one game released in the US, Batman: Return of the Joker. Many Japanese releases by Sunsoft used the FME-7: Gimmick!, Hebereke, Gremlins 2 (but not in the US version), Barcode World, and others.

The FME-7 has up to 6 bits for PRG banking (512 KiB), though this was never used in a game. The 5A and 5B, however, support only 5 (256 KiB). The extra address line is instead an audio expansion line, or unused.

It is confirmed that the FME-7 outputs the bank number during accesses to $6000-$7FFF even if RAM is enabled.
Though Sunsoft never took advantage of this, it would allow making a cartridge that bank switches up to 256 KiB of PRG RAM.
The FME-7 mapper in Loopy's PowerPak mappers, for example, supports 32 KiB.

Open bus occurs if the RAM / ROM Select Bit is 1 (RAM selected), but the RAM Enable Bit is 0 (disabled), i.e. any value in the range $40-$7F. This is a limited form of WRAM write protection on power-up.

NOTE: the enable bit is NOT functional with 2048×8, 32768×8, and 524288×8 RAMs, because those RAMs don't have a +CE input.

IRQ Counter Low Byte ($E)

IRQ Counter High Byte ($F)

Writes to the IRQ counter registers directly set the lower or upper eight bits of the counter. Unlike on MMC3, there is no separate reload latch.

IRQ Operation

The IRQ feature of FME-7 is a CPU cycle counting IRQ generator. When enabled the 16-bit IRQ counter is decremented once per CPU cycle. When the IRQ counter is decremented from $0000 to $FFFF an IRQ is generated. The IRQ line is held low until it is acknowledged.

How to Use the IRQ Generator

Set the counter to the desired number of cycles minus one.

Enable the IRQ generator by turning on both the IRQ Enable and IRQ Counter Enable flags of the IRQ Control command.

Within the IRQ handler, write to the IRQ Control command to acknowledge the IRQ.